The station first signed on the air on December 24, 1953 as KOA-TV. Founded by Metropolitan Broadcasting (partly owned by famed comedian Bob Hope),[1] owners of KOA radio (850 AM and 103.5 FM, now KRFX), channel 4 immediately assumed the NBC affiliation from KBTV (channel 9, now KUSA), due to KOA radio's longtime affiliation with and ownership by the NBC Red Network.

In 1965, KOA-TV began carrying most of NBC's American Football League game telecasts as the network obtained the league's broadcast television rights (with play-by-play announcing duties handled by Curt Gowdy); however, Denver Broncos home games aired by the network had to be blacked out due to the team's inability to sell out tickets to the games (NFL blackout rules in effect at the time required teams to sell all tickets for home games in order to allow them to be broadcast in the team's primary market, the league has since lowered the designated sales threshold to allow home game broadcasts to 75% of all tickets). In 1967, KOA-TV ran an award-winning documentary The Acid Test, LSD; hosted by news editor Bob Palmer, the film took five months to produce with more than 5,000 feet of film shot. Photographers involved included Bill Baker, Medill Barnes, Jerry Curran, Sam Houston and Barry Trader.

KOA-TV, which switched from logo to logo in the 1970s, stuck with this "circle 4" logo that was used until 1993.

In 1968, Metropolitan Broadcasting sold KOA-AM-TV to General Electric for $10 million. From 1972 to 1976, KOA-TV was carried by cable providers in the Rapid City, South Dakota area as NBC did not have an affiliate in that market.[citation needed] At the time, KOTA-TV maintained a dual primary affiliation with both ABC and CBS, leaving no room to carry NBC programs on its schedule; KEVN-TV (now a Fox affiliate), meanwhile, would not sign on until 1976, sharing the NBC affiliation with KOTA-TV until KEVN became an exclusive NBC affiliate in 1987. General Electric sold the KOA radio stations to A. H. Belo Corporation in 1983 for $22 million, as part of the company's overall exit from broadcasting. GE retained channel 4, but was required to change the station's call letters to KCNC-TV (standing for "Colorado's News Channel"), which it officially adopted on August 12 of that year.

On the evening of June 18, 1984, Alan Berg – an attorney who hosted programs on both KOA radio and KOA-TV and was known for taking a largely liberal stand on issues, using an abrasive and combative demeanor to callers and guests with opposing views at times – was shot and killed in the driveway of his home by members of a White Nationalist group called The Order.

In 1986, General Electric acquired NBC, resulting in KCNC becoming the first owned-and-operated station of a major network in the state of Colorado. By 1990, KCNC-TV devoted nearly all of its programming hours outside of network shows to locally-produced news programs, broadcasting nearly 40 hours of newscasts each week. General manager Roger Ogden felt his station's money was better spent on local programming, rather than paying syndication distributors to acquire nationally syndicated shows. In 1990, KCNC paid $11,000 to KRMA-TV (channel 6) in Denver to carry the station's election coverage (using KCNC's reporters), in order to allow channel 4 to air NBC's Tuesday night lineup, including Matlock and In the Heat of the Night.[2]

KCNC became Denver's CBS affiliate at 12:00 a.m. on September 10, 1995, as part of a three-way affiliation swap involving each of the market's "Big Three" network affiliates. Longtime CBS affiliate KMGH-TV (channel 7) switched its affiliation to ABC through a multi-station affiliation agreement with KMGH's owners at the time, McGraw-Hill; while longtime ABC affiliate KUSA took the NBC affiliation (although KUSA's owners, the Gannett Company, had already owned several NBC affiliates at the time, as is the case in the present day). The final NBC program broadcast on the station on September 9 was a repeat episode of Saturday Night Live; NBC moved all of its programming locally to KUSA after the program ended. Under the terms of the CBS/Westinghouse deal, CBS a sold controlling ownership interest (55%) in KCNC to Westinghouse's broadcasting division Group W. The previous month on August 1, Westinghouse had acquired CBS for $5.4 billion; once the merger was finalized on November 24, 1995, KCNC-TV became a CBS-owned-and-operated station, making it one of a handful of television stations that have been owned by two different networks at separate points in its history.[6] As of 2014[update], KCNC is the only television station in the Denver market that is an owned-and-operated station of one of the five major English language broadcast networks (at the time of the CBS-Westinghouse merger, Fox had acquired KDVR (channel 31), which it would eventually sell to Local TV in 2008).

In 1998, CBS acquired the broadcast rights to the American Football Conference of the National Football League (which absorbed the AFL and the Broncos in 1970), moving the conference's game telecasts to the network from NBC; as a result, KCNC regained the local television rights to the Broncos (coinciding with the season in which the team earned its second straight Super Bowl championship and fan favorite John Elway played his final season with the Broncos before his retirement from the NFL). In 2003, KCNC changed its on-air branding to "CBS 4" (the logo seen above similar how style that Los Angeles sister duopoly of KCBS-TV/KCAL-TV) to comply with the network mandated branding conventions (although it retained the longtime News 4 title for its newscasts until 2005, when the newscasts were rebranded as CBS 4 News).

The station was featured in the 2007 film Blades of Glory; along with other Denver area stations, it has also been mentioned on the Colorado-set Comedy Central series South Park. In one episode, Ron Zappolo is referenced as still being with channel 4 (although at the time, Zapollo served as evening anchor at KDVR).[7]

KCNC-TV shut down its analog signal, over VHF channel 4, on June 12, 2009, the official date in which full-power television stations in the United States transitioned from analog to digital broadcasts under federal mandate. The station's digital signal remained on its pre-transition UHF channel 35.[10] Through the use of PSIP, digital television receivers display the station's virtual channel as its former VHF analog channel 4.

On October 21, 2014, CBS and Weigel Broadcasting announced the launch of a new digital subchannel service called Decades, scheduled to launch on all CBS-owned stations in 2015, which KCNC-TV launched on channel 4.2 on January 23, 2015.[9] The channel is co-owned by CBS and Weigel (owner of CBS affiliate WDJT-TV in Milwaukee), with Weigel being responsible for distribution to non-CBS-owned stations. It airs programs from the extensive library of CBS Television Distribution, including archival footage from CBS News.[12]

KCNC-TV presently broadcasts 31 hours of locally-produced newscasts each week (with five hours on weekdays, 2½ hours on Saturdays and 3½ hours on Sundays); in addition, the station produces the sports highlight/discussion programs Saturday Sports Extra (which airs during the final 13 minutes of the Saturday edition of the 10:00 p.m. newscast) and AutoNation All Access (which airs after the Sunday edition of the 10:00 p.m. newscast).

In 1969, Bob Palmer, who served as anchor of the 10:00 p.m. newscast, left channel 4 for KLZ-TV (now KMGH-TV), to replace John Rayburn, who left for an anchor job at a station in Kansas City. In the 1970s, the station ran its late evening newscasts on weekends at 11:00 p.m. (one hour later than the typical late news timeslot in the Mountain Time Zone). In 1981, KBTV news director Roger Ogden was hired by KOA-TV as its general manager; during his tenure, Ogden hired Marv Rockford and John Haralson, who had both worked alongside Ogden at channel 9, to join the station's news staff. Ogden named George Caldwell, Sam Allred and Ron Zappolo as its main anchor team. Janet Zappala and Alan Berg joined the station as well that year. In 1983, Marv Rockford was promoted to the news director position; while Peter Rogot was named the station's weekend anchor and Marty Aarons joined Bob Palmer and Janet Zappala as anchors; other staffers that joined channel 4 during 1983 included Wendy Bergen, Karen Layton, Marcia Neville, Tom Raponi and Mike Silva.

In 1982, KMGH-TV anchor Bill Stuart left to join KOA-TV, joining several other new hires such as Linda Farrell, Sylvia Cordy, Jeff Hullinger, Stephanie White, Merrie Lynn, Tom Martino and Tom Bear. That June, KOA-TV debuted a half-hour 4:30 p.m. newscast titled First News, which was co-anchored by Larry Green and Linda Farrell, with Suzanne McCarroll as the featured reporter on the new show; the program would eventually expand to an hour-long broadcast beginning at 4:00 p.m., and remained on the station until it was cancelled on May 26, 2006 in order to air The Oprah Winfrey Show in the timeslot. Also that year, the station's news helicopter ("Copter 4") crashed into a snowy stand of pine trees near Larkspur, while en route to the crash site of a commuter airplane, killing KOA-TV pilot/reporter Karen Key (who was the first female pilot of a news helicopter in the country) and mechanic Larry Zane; autopsy results later reported that Key had a blood alcohol content at the time of the crash at 0.09 (just below the legal limit of 0.10).

In 2002, Marv Rockford was forced out as general manager of KCNC and replaced by Walt DeHaven. Meanwhile, Tony Lopez moved from San Antonio to join channel 4. In 2003, Molly Hughes and Bill Stuart served as KCNC's primary evening news team for its 10:00 p.m. newscast, with Brian Maass and Rick Sallinger as reporters. On April 21, 2008, Karen Leigh (who previously worked at Minneapolis sister station WCCO-TV) replaced Molly Hughes as co-anchor of the weeknight newscasts. KCNC also began broadcasting its local newscasts in high definition on that date, becoming the second television station in the Denver market (after KUSA) to make the conversion and the market's third station to broadcast all of its programming, including syndicated programs, in the format (behind KUSA and KTVD (channel 20)).

On May 27, 2010, KCNC implemented a new standardized graphics package for the CBS-owned stations, with the CBS Eye logo (includes the glass design) featured prominently in the package. KCNC retained 615 Music's Newstime as the theme music for its newscasts (whose used upon the 2003 station's rebranding) until October 6, 2011,[13] when the station began using Gari Media Group's CBS Enforcer News Music Collection (which the theme music based from "I Love Chicago, Chicago, My Home" signature) as most of CBS' other owned-and-operated stations (the theme's signature; when it was introduced by Chicago-sister station, WBBM-TV in the mid-1970s) did upon or before adopting the standardized graphics[14] (cuts from Newstime continue to be used for sponsor tags during the newscasts).

The 4:00 p.m. newscast returned to the schedule on June 13, 2011, only lasting less than three months before it was dropped a second time after the September 2, 2011 broadcast and replaced three days later by Dr. Phil.[15] On February 3, 2013, KCNC debuted a "Mobile Weather Lab," a technologically equipped Chevrolet Suburban (which is retrofitted for off-road use and is primarily used during the weekday morning newscasts; and the equipped-based model was manufactured by General Motors-owned Chevrolet) that is used for storm tracking and is equipped with a weather station that provides live data.[16] On January 13, 2014, KCNC expanded its weekday morning newscast to 2½ hours, with the addition of a half-hour at 4:30 a.m.